Hello
I have a job to make some stair treads. That normally means no issue but these are solid oak treads at 100mm thick and 235mm wide and roughly 800mm long. They will be put in between two steel U section strings my question is can I fit oak at that size and thickness tight in between these strings or do i need to leave and expatiation gap and if so how much of one for each side?

Also what could the effect be to the treads if fitter tight and they did expand ?

you could use brass or zinc as spacing
but dont forget all bolts or fixings must also be oak freindly
wood wont expand along its length so 3-5mm expansion each end is more than enough to allow the metal to move
are you remembering you need no gap greater than 95[100]mm in the riser assuming open ??

That staircase in my avatar is all steel. The oak treads (about 25mm thick) were fixed down using rubber grommets beneath the screws to ensure that there is minimal timber to steel contact, the screws the themselves were A2 stainless steel countersunk and pelleted and the steel was coated with an intumescent paint before it was finished with what smelled like an epoxy paint. We fixed with two screws at either end of the treads leaving about 3mm at each end of the treads (no more than that needed, really, as timber tends to expand and contract across the grain more than along the length) but the oak was sealed with 4 coats of Sadolin before installation and we didn't cut any to length ourselves.

big-all wrote:you could use brass or zinc as spacing
but dont forget all bolts or fixings must also be oak freindly
wood wont expand along its length so 3-5mm expansion each end is more than enough to allow the metal to move
are you remembering you need no gap greater than 95[100]mm in the riser assuming open ??

we are currently undecided with the riser if its kept open or we put something there but i do understand the regulations don't allow anything bigger than 99mm

...and why we have a 100mm rubber ball to check (same as the BCO might have). If you need to squeeze it just a bit to get it through then you're OK. TBH I've rarely come across a BCO who's so pedantic that he'd jump up and down about 2mm - in the case of steel staircases you've got far greater problems to deal with getting the treads level side-to-side and front-to-back as well as with an even rise between treads. The last one I did, in fact four separate rises, was all over the show when we started and made worse by the attempt to weld several tons of ballasting onto the stringers of the longest section to damp the bounciness which it had. I needed to level off each and every tread on the four flights. Reckon that welding all the extra steel must have twisted the whole lot

"The person who never made a mistake, never made anything" - Albert Einstein

"I too will something make, And joy in the making" - Robert Bridges, 1844~1930